Cement admixture, cement composition, and cement concrete made therefrom

ABSTRACT

A cement admixture of a low environmental load type, capable of reducing hexavalent chromium, having a small slump loss or heat of hydration, hardly neutralized and capable of suppressing autogenous shrinkage to a low level; a cement composition; and cement concrete employing it, are presented. The cement admixture comprises a slowly cooled slag powder which contains melilite as the main component and which has a carbon dioxide absorption of at least 2%, has a CO 2  absorption of at least 2%, has a loss on ignition of at most 5%, contains at least 0.5% of sulfur present as non-sulfuric acid form sulfur and/or has a concentration of non-sulfuric acid form sulfur to elute, of at least 100 mg/l, and further, preferably, has a degree of vitrification of at most 30%, a melilite lattice constant a of from 7.73 to 7.82 and/or a Blaine specific surface area of at least 4,000 cm 2 /g.

TECHNICAL FIELD

The present invention relates to a cement admixture, a cementcomposition and cement concrete made thereof, which are to be usedmainly in the field of civil engineering and construction. Here, cementconcrete used in the present invention generally refers to cement paste,mortar and concrete. Further, parts or % in the present invention are bymass unless otherwise specified.

BACKGROUND ART

With respect to carbon dioxide emission, the proportion of civilengineering and construction in overall industry is very large, and itis desired to reduce its environmental load. On the other hand, carbondioxide discharged from cement industry derives mostly from fuel duringcalcination or from decarboxylation of limestone as the startingmaterial. Accordingly, in order to reduce the carbon dioxide emission,it is the most effective method to reduce the calcination amount ofcement clinker, and it is extremely important to promote utilization ofvarious mixed cements.

Further, with a view to constructing durable concrete structures, it isdesired to prevent bleeding resulting from segregation and to suppressheat generation by hydration. Particularly, in recent years, theperformance required for concrete is diversified, and for the purpose ofrationalization of application, various types of high fluidity concretehave been proposed which require no compaction and which haveself-filling properties (“Report I of JCI Ultra Fluidity ConcreteResearch Committee” (May 1003) and “Report II of the same” (May 1994),published by Japan Concrete Institute).

Such high fluidity concrete tends to undergo segregation if the unitquantity of a binder such as cement is less than about 500 kg/m³, andaccordingly, it usually has a unit binder quantity of at least about 500kg/m³. And, high fluidity concrete having a large unit binder quantityhas a problem that the hydration heat value is large and theenvironmental load is also large.

In order to solve such a problem, high fluidity concrete has beenproposed in which fine powder of limestone is used in substitution for apart of the binder (JP-A-5-319889). The fine powder of limestone showsno substantial hydraulicity, and accordingly, the high fluidity concretein which fine powder of limestone is used in substitution for a part ofthe binder, has a merit such that it imparts segregation resistancewithout bringing about unnecessary heat of hydration. However, limestoneis a valuable natural resource for our country having small resources,and its utilization merely for admixing it to concrete, is likely tolead to depletion of the resource. Accordingly, there are presently manyvoices for more effective utilization of limestone.

Further, limestone-admixed cement has a problem that it is likely to beneutralized, and it is poor in providing initial strength.Neutralization is important since it relates to durability of aferroconcrete structure, and the initial strength is important, since itdeeply relates to unmold cycle and thus is important for shortening theapplication period. Further, the neutralization is an importantdeterioration factor influential over the durability of ferroconcrete,and in neutralized concrete, the reinforcing steel will be corroded, andthere will be a danger of falling of concrete fragments. At present, itis desired to develop a cement composition which is excellent inproviding durability and initial strength and which is capable ofproviding strength equal to one where usual Portland cement is usedalone, even if the admixture is used in combination in an amountexceeding 30%.

On the other hand, blast furnace slag discharged as industrial wastefrom steel plants is widely used in the cement concrete field. The blastfurnace slag is generally classified into quenched and vitrifiedso-called granulated blast furnace slag and air-cooled and crystallizedso-called slowly cooled blast furnace slag. Among them, the granulatedblast furnace slag has alkali latent hydraulicity, and one pulverized tothe same level as cement, or more finely than cement, is used as astarting material for blast furnace cement.

Vitrified granulated blast furnace slag has excellent latenthydraulicity whereby even when admixed in a large amount to cementclinker, its long term strength will not decrease, and its studies arebeing made in various fields of e.g. high strength concrete and highfluidity concrete (“Applicability of Fine Powder of Blast Furnace Slagto High Strength Concrete”, Kenichi Yasudo et al., papers reported atthe 45th Cement Technology Convention, pp. 184-189, 1991, etc.).

The vitrified granulated blast furnace slag has excellent latenthydraulicity whereby the strength will not decrease for a long period oftime even when it is admixed in a large amount to cement clinker.However, on the other hand of exhibiting such high strength, thevitrified granulated blast furnace slag has had a problem such that heatgeneration by hydration and autogenous shrinkage tend to be substantial.Such heat generation and autogenous shrinkage are factors which inducecracking, and they are phenomena not desirable when durableferroconcrete structures are to be constructed.

On the other hand, slowly cooled blast furnace slag is called also byanother name i.e. crystallized slag or ballas and is one showing nohydraulicity. Accordingly, it was used mainly as a roadbed material, butrecently, reclaimed aggregate has become to be preferentially used as aroadbed material. Thus, it is likely to lose the conventionalapplication, and its useful application is still being sought(“Application of Blast Furnace Slag to Cement Concrete”, Akihiko Yoda,Inorganic material, Vol. 6, pp. 62-67, 1999), “Law Relating to Promotionof Utilizing Reclaimed Resource, so-called recycle law”, October 1991).

In recent years, a problem relating to durability of concrete has beentaken up as a serious problem, and guidelines, principles forstandardization, etc., relating to durable concrete have been publishedby various academic societies. Particularly, the water/cement ratio ofconcrete is substantially influential over the durability, andaccordingly, for the purpose of reducing the unit quantity of water,frequency of use of a high performance water reducing agent or a highperformance AE water reducing agent has rapidly increased, andguidelines therefor have also been issued.

However, there is a problem such that as the unit quantity of water isreduced, the change with time of consistency tends to be large, and thefluidity tends to decrease, and at present, there is no fundamentalsolution to this problem. It is particularly in the case of highfluidity concrete that the problem of the fluidity decrease is taken upas a serious problem.

High fluidity concrete is a concrete developed not to be susceptible toan influence due to the quality of workmanship, and its self-fillingproperty is the most important characteristic. And it is required tomaintain the fluidity during the transportation from the ready-mixedconcrete plant to the application site and further for a certain periodat the application site. However, due to some troubles at theapplication site or a traffic jam during the transportation, it mayfrequently take time over the prescribed time, whereby the fluidity ofconcrete tends to be outside the prescribed standard.

In such a case, there is no other means than carrying out so-calledre-fluidizing treatment i.e. by additionally adding a high performanceAE water reducing agent or the like to have it re-fluidized. However, atpresent, such re-fluidizing treatment can be done only by a skilledhand. Accordingly, it is strongly desired to develop concrete excellentin the fluidity-maintaining performance.

On the other hand, from the viewpoint of an environment problem, a largeexpectation is present with respect to reduction of hexavalent chromiumwhich presents adverse effects against human bodies. A method has beenproposed to reduce the amount of elution of hexavalent chromium by areducing agent or adsorbent thereof. However, such a material is tooexpensive to be used in the field of cement concrete and is notsubstantially practically used.

Under these circumstances, the present inventors have conducted variousstudies on effective utilization of slowly cooled blast furnace slag andas a result, have found that a slowly cooled blast furnace slag powderhas a function of suppressing neutralization, is excellent in theperformance in maintaining fluidity and segregation resistance, hassmall-autogenous shrinkage and can be made to be high fluidity concretehaving low heat generation by hydration, and shows an effect to reducehexavalent chromium under a prescribed condition, and further, by usinga cement composition comprising a Portland cement having a C₃S contentof at least 60% and a slowly cooled blast furnace slag powder, it ispossible to make a cement composition excellent in the initialstrength-providing property and having little environmental load,whereby the conventional problems can be solved, and the presentinvention has been accomplished.

DISCLOSURE OF THE INVENTION

Namely, the present invention has the following construction.

(1) A cement admixture characterized by comprising a slowly cooled blastfurnace slag powder which contains melilite as the main component andhas a carbon dioxide absorption of at least 2% when carbonated for 7days in the air having a carbon dioxide concentration of 5%, atemperature of 30° C. and a relative humidity of 60%.

(2) A cement admixture characterized by comprising a slowly cooled blastfurnace slag powder which contains melilite as the main component andhas a loss on ignition of at most 5%, which is a weight reduction whenignited at 1,000° C. for 30 minutes.

(3) A cement admixture characterized by comprising a slowly cooled blastfurnace slag powder which contains melilite as the main component andcontains at least 0.5% of sulfur present as non-sulfuric acid formsulfur.

(4) A cement admixture characterized by comprising a slowly cooled blastfurnace slag powder which contains melilite as the main component andhas an ion concentration of non-sulfuric acid form sulfur to elute, ofat least 100 mg/l.

(5) The cement admixture according to any one of (1), (3) and (4), whichcomprises the slowly cooled blast furnace slag powder which containsmelilite as the main component and has a loss on ignition of at most 5%,which is a weight reduction when ignited at 1,000° C. for 30 minutes.

(6) The cement admixture according to any one of (1), (2), (4) and (5),which comprises the slowly cooled blast furnace slag powder whichcontains melilite as the main component and contains at least 0.5% ofsulfur present as non-sulfuric acid form sulfur.

(7) The cement admixture according to any one of (1) to (3), (5) and(6), which comprises the slowly cooled blast furnace slag powder whichcontains melilite as the main component and has a concentration ofnon-sulfuric acid form sulfur to elute, of at least 100 mg/l.

(8) The cement admixture according to any one of claims 1 to 7, whichcomprises the slowly cooled blast furnace slag powder having a degree ofvitrification of at most 30%.

(9) The cement admixture according to any one of (1) to (8), whichcomprises the slowly cooled blast furnace slag powder having a melilitelattice constant a of from 7.73 to 7.82.

(10) The cement admixture according to any one of (1) to (9), whichcomprises the slowly cooled blast furnace slag powder having a Blainespecific surface area of at least 4000 cm²/g.

(11) The cement admixture according to any one of (1) to (10), which hasan oxygen consumption of at least 2.5×10⁻³ mmolO₂/g.

(12) The cement admixture according to any one of (1) to (10), which hasan oxidation-reduction potential of at least 100 mV.

(13) A cement composition containing the cement admixture as defined inany one of (1) to (12).

(14) The cement composition according to (13), wherein the cement isPortland cement having a 3CaO.SiO₂ content of at least 60 wt %.

(15) Cement concrete made of the cement composition as defined in (13)or (14).

(16) The cement concrete according to (15), which has a slump flow of650±50 mm.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, the present invention will be described in detail.

The slowly cooled blast furnace slag powder (hereinafter referred toalso simply as the slowly cooled slag powder) to be used in the presentinvention is an air-cooled and crystallized blast furnace slag powder.The components of the slowly cooled slag powder have the samecomposition as the granulated blast furnace slag, and specifically, itcomprises SiO₂, CaO, Al₂O₃ and MgO as the main chemical components andmay contain, for example, TiO₂, MnO, Na₂O, S, P₂O₅ and Fe₂O₃ as othercomponents.

Further, the slowly cooled slag powder contains so-called melilite asthe main component which is mixed crystal of gehlenite 2CaO.Al₂O₃.SiO₂and akermanite 2CaO.MgO.2SiO₂ and further may contain others i.e.calcium silicates such as dicalcium silicate 2CaO.SiO₂, rankinite3CaO.2SiO₂ and wollastonite CaO.SiO₂, calcium magnesium silicates suchas merwinite 3CaO.MgO.2SiO₂ and monticellite CaO.MgO.SiO₂, anorthiteCaO.Al₂O₃.2SiO₂, leucite (K₂O, Na₂O).Al₂O₃.SiO₂, spinel MgO.Al₂O₃,magnetite Fe₃O₄, and a sulfide such as calcium sulfide CaS or ironsulfide FeS.

The slowly cooled slag powder to be used in the present inventioncontains melilite as the main component, and its carbon dioxideabsorption (hereinafter referred to as the CO₂ absorption) is at least2%. The CO₂ absorption of the slowly cooled slag powder is at least 2%,preferably at least 3%, more preferably at least 4%. If the CO₂absorption is less than 2%, the effect for suppressing theneutralization will not be adequate, and there may be a case where noadequate effects of the present invention can be obtained.

The CO₂ absorption means the carbon dioxide absorption whencarbonization is carried out for seven days in the air having a carbondioxide gas concentration of 5%, a temperature of 30° C. and a relativehumidity of 60%. In such a case, there may be a case where the is sampleprior to carrying out carbonization treatment may contain carbondioxide, and accordingly, it may be represented by the formula of(carbon dioxide absorption)=(the carbon dioxide amount of the sampleafter the carbonization treatment)−(the carbon dioxide amount of thesample prior to the carbonization treatment).

The CO₂ absorption can be obtained by quantifying the amount of carbonby the total carbon analysis and converting it to the CO₂ amount.Otherwise, it can be obtained also by e.g. a thermal analysis (TG-DTA orDSC).

Further, the loss on ignition (hereinafter referred to also as the boundwater amount) of the slowly cooled slag powder is at most 5%. The boundwater amount of the slowly cooled slag powder is at most 5%, preferablyat most 4%, more preferably at most 3%. If the bound water amountexceeds 5%, excess strength, or the accompanying heat generation byhydration or autogenous shrinkage, tends to increase, and there may be acase where no adequate effects of the present invention will beobtained. The loss on ignition usually means a weight reduction when asample is ignited at 1,000° C. for 30 minutes and is regarded as a boundwater amount of a hydrated sample.

Pretreatment of a sample is carried out by removing excess water from ahydrated sample by a large amount of acetone, an alcohol or the like,followed by drying. The drying is carried out under such a dryingcondition that a part of the bound water of the hydrate will not beremoved. For example, drying under reduced pressure is carried out by anaspirator to a constant weight.

Sulfur present as non-sulfuric acid form sulfur in the slowly cooledslag powder (hereinafter referred to simply as non-sulfuric acid formsulfur) is at least 0.5%. Here, the non-sulfuric acid form sulfur ismeant for sulfur in a non-sulfuric acid form, such as a sulfide, apolysulfide, sulfur, thiosulfuric acid and sulfurous acid. Thenon-sulfuric acid form sulfur is at least 0.5%, preferably at least0.7%, more preferably at least 0.9%. If the non-sulfuric form sulfur isless than 0.5%, there may be a case where no adequate effect of thepresent invention i.e. no adequate fluidity-maintaining performance orhexavalent chromium-reducing performance can be obtained.

The amount of the non-sulfuric acid form sulfur may be obtained bydeducting the amount of sulfuric acid sulfur (sulfur trioxide) from thetotal sulfur amount, or it may be obtained as the sum of amounts ofnon-sulfuric acid form sulfurs such as thiosulfuric acid form sulfur andsulfurous acid sulfur. Such an amount may be obtained by quantifying bya method of Yamaguchi and Ono (“State Analysis of Sulfur in BlastFurnace Slag”, Naoharu Yamaguchi and Akihiro Ono; Study on Steel Making,No. 301, pp. 37-40, 1980) or by quantifying by the method prescribed inJIS R 5202.

The slowly cooled slag powder exhibits the fluidity-maintainingperformance and the effect of reducing hazardous heavy metals includinghexagonal chromium, by containing the non-sulfuric acid form sulfur.However, even if a polysulfide, a sulfide, a thiosulfate, and a sulfite,etc. are merely added to slag not containing non-sulfuric acid formsulfur, it is not possible to obtain the fluidity-maintaining effectexcellent in durability or the effect for reducing hazardous heavymetals such as hexagonal chromium, of the present invention. Thehazardous heavy metals meant by the present invention include, forexample, hexagonal chromium, lead, cadmium, nickel, mercury, arsenic,selenium, molybdenum, etc.

The amount of the reducing agent to be used is preferably from 1 to 50parts by weight, particularly preferably from 5 to 40 parts by weight,per 100 parts by weight of the total of the slag powder and the reducingagent. If it is less than 1 part by weight, no adequate effect of thecombined use will be obtained. On the other hand, if it exceeds 50 partsby weight, the cost increases, such being undesirable.

However, within a range not to impair the purpose of the presentinvention, it is preferred to use in combination various releasingagents which are commonly used as hexagonal chromium-reducing materials.Specifically, sulfides such as ammonium sulfide, calcium sulfide, coppersulfide, nickel sulfide, zinc sulfide, antimony sulfide, zirconiumsulfide, sodium hydrogen sulfide, lithium hydrogen sulfide and ammoniumpolysulfide, sulfites such as potassium sulfite, ammonium sulfite,sodium sulfite, calcium sulfite, sodium sulfite and potassium hydrogensulfite, thiosulfates such as sodium thiosulfate and potassiumthiosulfate, sulfide compounds such as sulfur dioxide or sulfur, andferrous sulfate, may, for example, be mentioned. Among them, ferroussulfate is particularly effective.

Further, in the present invention, the ion concentration of non-sulfuricacid form sulfur which elutes from the slowly cooled slag powder(hereinafter referred to as the soluble sulfur concentration) is atleast 100 mg/l. The soluble sulfur concentration is particularlypreferably at least 150 mg/l. If the soluble sulfur concentration isless than 100 mg/l, there may be a case where no adequatefluidity-maintaining property or hexavalent chromium-reducing effect ofcement concrete can be obtained.

Ions of non-sulfuric acid form sulfur may, for example, be sulfur ions(S²⁻), polysulfide ions (S_(n) ²⁻, n≧2), thiosulfate ions (S₂O₃ ²⁻),sulfite ions (SO₃ ²⁻) and sulfate ions (SO₄ ²⁻). The soluble sulfurconcentration is the concentration of non-sulfuric acid form sulfur ionscontained in the liquid phase, when 20 g of the slowly cooled slagpowder is put into 100 ml of water at 20° C. and stirred for 30 minutes,followed by solid-liquid separation. Such a sulfur concentration can bequantified by an ICP emission spectrometry or by an ion chromatography.

The degree of vitrification of the slowly cooled slag powder ispreferably at most 30%, more preferably at most 10%. If the degree ofvitrification exceeds 30%, the heat of hydration is likely to increase,whereby there may be a case where the prescribed fluidity-maintainingperformance, hexavalent chromium-reducing effects,neutralization-suppressing effects and effects to suppress heatgeneration by hydration cannot be obtained.

If the degree of vitrification is high, even if substantially the sameamount of non-sulfuric acid form sulfur is contained, elution of e.g.thiosulfate sulfur is extremely little as compared with the crystallineslowly cooled slag, and the fluidity-maintaining performance or thehexavalent chromium-reducing effects are small. Further, as the degreeof vitrification increases, there may be a case where heat generationaccompanied by hydration will result.

Further, the neutralization-suppressing effects are also a naturecharacteristic to a crystalline substance. Accordingly, no such effectsare likely to be observed as the degree of vitrification increases. Thevitrification degree (X) is obtained by X(%)=(1−S/S₀)×100. Here, S isthe area of the main peak of melilite as the main crystalline compoundin the slowly cooled slag powder, as obtained by the powder X-raydiffraction method, and S₀ is the area of the main peak of melilite inthe product obtained by heating the slowly cooled slag powder at 1,000°C. for 3 hours, followed by cooling at a cooling rate of 5° C./min.

Further, the lattice constant a of mielilite of the slowly cooled slagpowder is preferably from 7.73 to 7.82. The slowly cooled slag powderhaving the lattice constant a of melilite within this range isparticularly preferred, since the neutralization-suppressing effects areremarkable. It is particularly preferred that the lattice constant a isfrom 7.75 to 7.80.

The Blaine specific surface area value (hereinafter also referred tosimply as the Blaine value) of the slowly cooled slag powder is notparticularly limited, but it is preferably at least 4,000 cm²/g, morepreferably from 4,500 cm²/g to 8,000 cm²/g, most preferably from 5,000cm²/g to 8,000 cm²/g. If the Blaine value is less than 4,000 cm²/g,there may be a case where the segregation resistance tends to be hardlyobtainable, no adequate neutralization-suppressing effects can beobtained, or no adequate fluidity-maintaining performance or hexavalentchromium-reducing performance can be obtained. If it is pulverized toexceed 8,000 cm²/g, the pulverization power is required to be large,such being uneconomical, and the slowly cooled slag powder is likely tobe weathered, and there may be a case where deterioration with time ofthe quality tends to increase.

By this particle size, it is possible to control the amount of elutionof thiosulfate sulfur, sulfite sulfur or the like. By increasing thefineness, the initial fluidity, the hexavalent chromium-reducing effectsand neutralization-suppressing effects can be increased, and inversely,by decreasing the fineness, it becomes possible to present thefluidity-maintaining performance, the hexavalent chromium-reducingeffects and the neutralization-preventing effects over a long period oftime.

The oxygen consumption of the slowly cooled slag powder is preferably atleast 2.5×10⁻³ mmolO₂/g, more preferably at least 3.0×10⁻³ mmolo₂/g. Ifit is less than 2.5×10⁻³ mmolO₂/g, there may be a case where no adequatefluidity of cement concrete or hexavalent chromium-reducing effects canbe obtained.

The oxygen consumption is an index to show the reducing ability of theslag powder. For example, 2 g of a slag powder and 40 ml of distilledwater are mixed, shook for 2 hours and then subjected to filtration. To10 ml of the filtrate, 10 ml of a 0.1 mol/l tetravalent cerium sulfateaqueous solution and a few drops of a 1/40 mol/l oxidation-reductionindicator ferroin are added, and tetravalent cerium remaining in theshaken liquid is titrated with 0.1 mol/l ferrous sulfate. From thisvalue, the amount of tetravalent cerium (unit: mmol/g) reduced totrivalent by the slag powder is obtained, and one dividing this value by4 is taken as the oxygen consumption (unit: mmolO₂/g).

The oxidation-reduction potential of the slowly cooled slag powder ispreferably at least 100 mV, more preferably at least 150 mV. If it isless than 100 mV, there may be a case where no adequate hexavalentchromium-reducing effects can be obtained. The oxidation-reductionpotential is one of indices showing the reducing ability of the slagpowder. For example, 50 g of a slag powder and 100 ml of distilled waterare mixed, shook for 24 hours and then subjected to filtration. Theoxidation-reduction potential of the filtrate is measured by aprescribed ORP electrodes to obtain ORP1. Then, the pH of this filtrateis measured, and the oxidation-reduction potential ORP2 of distilledwater adjusted to the same pH, is measured. The difference between ORP2and ORP1 (ORP2-ORP1) is taken as the oxidation-reduction potential(unit: mV).

The cement admixture of the present invention (hereinafter referred tosimply as the present admixture) comprises a slowly cooled slag powderwhich contains melilite as the main component and has a carbon dioxideabsorption of at least 2% and a loss on ignition of at most 5%, containsat least 0.5% of sulfur present as non-sulfuric acid form sulfur, andhas a concentration of non-sulfuric acid form sulfur to elute, of atleast 100 mg/l, further preferably, a slowly cooled slag powder whichhas a degree of vitrification of at most 30%, a lattice constant a ofmelilite of from 7.73 to 7.82, and/or a Blaine specific surface area ofat least 4,000 cm²/g.

The Blaine value of the present admixture is not particularly limited,but it is preferably at least 4,000 cm²/g, more preferably from 4,500cm²/g to 8,000 cm²/g, most preferably from 5,000 cm²/g to 8,000 cm²/g.If the Blaine value is less than 4,000 cm²/g, there may be a case whereno adequate effects of the present invention can be obtained, and if itis pulverized to exceed 8,000 cm²/g, the pulverization power is requiredto be large, such being uneconomical, and the slowly cooled slag powderis likely to be weathered, and there may be a case where deteriorationwith time of the quality tends to be substantial.

The amount of the present admixture to be used, is not particularlylimited, but it is usually preferably from 3 to 60 parts, morepreferably from 5 to 50 parts, most preferably from 10 to 40 parts, in100 parts of the cement composition comprising cement and the presentadmixture. If it is less than 3 parts, no adequate effects of thepresent invention such as to reduce the heat of hydration or to improvethe fluidity-maintaining property, and if it is used in excess of 60parts, there may be a case where the strength-providing property tendsto be poor.

Here, as the cement, various Portland cements such as ordinary,high-early-strength, ultra high-early-strength, low heat andmoderate-heat, Portland cements, various blended cements havinggranulated blast furnace slag, fly ash or silica blended to suchPortland cements, and a filler cement having limestone powder mixed,may, for example, be mentioned. One or more of them may be used.

In the present invention, it is possible to obtain a cement compositionexcellent in the initial strength-developing property by combining thepresent admixture with a Portland cement having a 3CaO.SiO₂ (C₃S)content of at least 60 wt %. Usually, the Portland cement is constitutedby gypsum and clinker composed mainly of 2CaO.SiO₂ (C₂S), C₃S,3CaO.Al₂O₃ (C₃A) and 4CaO.Al₂O₃.Fe₂O₃ (C₄AF).

The Portland cement having a C₃S content of at least 60% of the presentinvention is not particularly limited, and a commercially availablehigh-early-strength cement or ultrahigh-early-strength cement may, forexample, be used. Further, the particle size of the Portland cementhaving a C₃S content of at least 60%, is not particularly limited, butit is usually preferably at a level of from 3,000 to 8,000 cm²/g by aBlaine value. If the Blaine value is less than 3,000 cm²/g, no adequateearly strength developing property may sometimes be obtainable, and forpulverization to exceed 8,000 cm²/g, the pulverization power tends to beextremely large, such being uneconomical, and the operation efficiencymay be likely to be poor.

The cement composition of the present invention is one comprising cementand the present admixture. For the cement composition of the presentinvention, the respective materials may be mixed at the time of theapplication, or a part or whole thereof may be preliminarily mixed. Forexample, a slowly cooled slag powder, cement clinker and gypsum mayseparately be pulverized and mixed, or a part or whole of them may bemixed and pulverized.

The particle size of the cement composition of the present invention isnot particularly limited, since it depends on the particular purpose orapplication. Usually, it is preferably from 3,000 to 8,000 cm²/g, morepreferably from 4,000 to 6,000 cm²/g, by a Blaine value. If it is lessthan 3,000 cm²/g, there may be a case where no adequatestrength-developing property can be obtained, and if it exceeds 8,000cm²/g, there may be a case where the operation efficiency tends to bepoor.

The cement composition of the present invention has a self-fillingproperty requiring no conventional shaking compaction and can be used ashigh fluidity concrete free from segregation, whereby the slump flowvalue as an index of fluidity is preferably 650±50 mm. If the slump flowvalue is less than 600 mm, the self-filling property is likely to beinadequate due to a change with time when the time required for theapplication or transportation is taken into account, and if it exceeds700 mm, there may be a case where segregation is likely to result.

When high fluidity concrete is to be prepared, it is preferred to employa water reducing agent such as a usual water reducing agent, an AEreducing agent, a high performance reducing agent or a high performanceAE reducing agent, for high fluidity. The water reducing agent iscommercially available in the form of a liquid or powder, and either onemay be used. Water reducing agents may be generally classified into anaphthalene type, a melamine type, an amino sulfonic acid type and apolycarboxylic acid type.

In the present invention, it is particularly preferred to use a highperformance AE reducing agent, and its specific examples include, forexample, a naphthalene type, such as “Rheobuild SP-9 Series”, tradename, manufactured by NMB Co., Ltd., “Mighty 2000 Series”, trade name,manufactured by Kao Corporation and “Sunflow HS-100”, trade name,manufactured by Nippon Paper Industries Co., Ltd. Further, as a melaminetype, “Sikament 1000 Series”, trade name, manufactured by Sika Ltd., or“Sunflow HS-40”, trade name, manufactured by Nippon Paper IndustriesCo., Ltd., may, for example, be mentioned.

Further, as the aminosulfonic acid type, “Palic FP-200 Series”, tradename, manufactured by Fujisawa Pharmaceutical Co., Ltd., may, forexample, be mentioned. And as the polycarboxylic acid type, “RheobuildSP-8 Series”, trade name, manufactured by NMB Co., Ltd., “Darex Super100PHX”, trade name, manufactured by W. R. Grace & Co., and “Chupol HP-8Series” or “Chupol HP-11 Series”, trade name, manufactured by TakemotoOil & Fat Co., Ltd., may, for example, be mentioned.

In the present invention, one or more of these water reducing agents canbe used. The amount of the water reducing agent to be used, is notparticularly limited. However, usually, it may be used within a rangewhich is specified by each manufacturer, and specifically, it is at alevel of from 0.5 to 3.0 parts per 100 parts of the cement compositioncomprising cement and the present admixture.

In the present invention, the amount of water to be used, is notparticularly limited. However, usually, it is preferably from 125 to 225kg, more preferably from 140 to 185 kg, per 1 m³ of the cement concrete.If it is less than 125 kg, the operation efficiency is likely to bepoor, and if it exceeds 185 kg, the dimensional stability,strength-developing property and durability are likely to be poor.

In the present invention, in addition to the cement, the presentadmixture, aggregates such as sand or gravel, and the water reducingagent, one or more may be used within a range not to substantiallyimpair the purpose of the present invention, among additives such asgranulated blast furnace slag powder, fine limestone powder, fly ash andsilica fume, a defoaming agent, a thickener, a rust-preventive agent, anantifreezer, a shrinkage-reducing agent, a polymer emulsion, a settingmodifier, a clay mineral such as bentonite, and an anion exchanger suchas hydrotalcite, which used to be employed for e.g. high fluidityconcrete.

In the present invention, the method for mixing various materials is notparticularly limited, and the respective materials may be mixed at thetime of the application, or a part or whole may be preliminarily mixed.As the mixing apparatus, any conventional apparatus may be used. Forexample, it is possible to use a tilting mixer, an omini mixer, aHenschel mixer, a V-form mixer and Nauta mixer.

Now, the present invention will be described in detail with reference toExamples.

TEST EXAMPLE 1

Concrete having an air amount of 4.5±1.5% and s/a=46% was prepared byusing the concrete blend composition as shown in Table 1 comprisingcement A, water, sand, gravel and various slag powders as the cementadmixture, and the slump loss, compression strength, adiabatictemperature increase and neutralization depth were measured.

Further, comparison was carried out with a blend composition by mixingfine limestone powder instead of the slag powder to obtain an equalcompression strength with the same blend proportions. The results areshown also in Table 1. Further, a water reducing agent was used so thatthe slump value of the concrete would be 18±1.5 cm.

Materials used Cement A: Ordinary Portland cement manufactured by DenkiKagaku Kogyo Kabushiki Kaisha, C₃S content: 55%, Blaine value: 3,200cm²/g, density: 3.15 g/cm³ Slag powder (1): Slowly cooled slag powder,CO₂ absorption: 2%, amount of bound water: 2%, degree of vitrification:5%, melilite lattice constant a: 7.78, Blaine value: 4,000 cm²/g,density: 3.00 g/cm³ Slag powder (2): Slowly cooled slag powder, CO₂absorption: 3%, amount of bound water: 2.5%, degree of vitrification:5%, melilite lattice constant a: 7.78, Blaine value: 4,500 cm²/g,density: 3.00 g/cm³ Slag powder (3) Slowly cooled slag powder, CO₂absorption: 3.5%, amount of bound water: 2.7%, degree of vitrification:5%, melilite lattice constant a: 7.78, Blaine value: 5,000 cm²/g,density: 3.00 g/cm³ Slag powder (4): Slowly cooled slag powder, CO₂absorption: 4%, amount of bound water: 3%, degree of vitrification: 5%,melilite lattice constant a: 7.78, Blaine value: 6,000 cm²/g, density:3.00 g/cm³ Slag powder (5): Slowly cooled slag powder, CO₂ absorption:4.5%, amount of bound water: 4%, degree of vitrification: 5%, melilitelattice constant a: 7.78, Blaine value: 8,000 cm²/g, density: 3.00 g/cm³Slag powder (6): Slowly cooled slag powder, CO₂ absorption: 3.5%, amountof bound water: 3%, degree of vitrification: 10%, melilite latticeconstant a: 7.76, Blaine value: 6,000 cm²/g, density: 2.97 g/cm³ Slagpowder (7): Slowly cooled slag powder, CO₂ absorption: 3%, amount ofbound water: 5%, degree of vitrification: 30%, melilite lattice constanta: 7.74, Blaine value: 6,000 cm²/g, density: 2.94 g/cm³ Slag powder (8):Slowly cooled slag powder, CO₂ absorption: 1%, amount of bound water:9.5%, degree of vitrification: 95%, Blaine value: 6,000 cm²/g, density:2.90 g/cm³ Water: Tap water Sand: Produced in Himekawa, NiigataPrefecture; density: 2.62 g/cm³ Gravel: Produced in Himekawa, NiigataPrefecture; crushed stone, density: 2.64 g/cm³ Water reducing agent:High performance AE water reducing agent, polycarboxylic acid type,commercial product Measuring methods Slump loss: A slump value wasmeasured in accordance with JIS A 1101, and from the slump valueimmediately after mixing, the slump value upon expiration of 90 minuteswas deducted to obtain the slump loss value. Compressing strength: Asample of 10φ × 20 cm was prepared, and the compression strength of thematerial age of 29 days was measured in accordance with JIA A 1108.Diabatic temperature Measured by means of an adiabatic increase:temperature increase- measuring apparatus manufactured by Tokyo RikoK.K. under a condition of a working temperature of 20° C. Neutralizationdepth: A sample of 10φ × 20 cm was prepared and aged in water of 20° C.till a material age of 28 days, whereupon accelerated neutralization wascarried out in an environment having a temperature of 30° C., a relativehumidity of 60% and a carbon dioxide gas concentration of 5%, and uponexpiration of 6 months, the sample was cut into round slices, whereby aphenolphthalein alcohol solution was coated on the cross-section toconfirm the neutralization depth.

TABLE 1 Unit weight (kg/cm³) Adiabatic Test Slag Slump Compressiontemperature Neutralization No. Cement Water Sand Gravel powder lossstrength increase depth Notes 1-1 245 175 804 951 (1)105 9.5 24.0 34.027.0 Ex. 1-2 245 175 804 951 (2)105 8.5 24.2 34.3 23.5 Ex. 1-3 245 175804 951 (3)105 7.5 24.3 34.5 19.5 Ex. 1-4 245 175 804 951 (4)105 7.024.4 34.8 18.5 Ex. 1-5 245 175 804 951 (5)105 6.0 24.9 34.9 16.0 Ex. 1-6245 175 804 951 (6)105 8.0 25.1 35.3 17.0 Ex. 1-7 245 175 803 950 (7)1059.5 26.2 37.0 17.5 Ex. 1-8 245 175 803 950 (8)105 11.5 33.9 44.2 — Comp.Ex. 1-9 350 175 806 954 — 0 12.0 33.5 45.5 — Comp. Ex. 1-10 339 175 806954 (4)11  11.5 33.2 44.1 — Ex. 1-11 332 175 806 954 (4)18  10.5 32.843.5 — Ex. 1-12 315 175 805 953 (4)35  9.5 30.7 41.4 — Ex. 1-13 280 175805 952 (4)70  8.5 27.5 37.8 — Ex. 1-14 210 175 803 950 (4)140 6.0 22.331.0 — Ex. 1-15 175 175 803 950 (4)175 5.0 20.3 28.2 — Ex. 1-16 140 175802 949 (4)210 4.0 18.0 25.0 — Ex. 1-17 245 175 804 951 * 105 11.5 24.834.5 42.5 Comp. Ex. Symbol * for slag powder means fine limestonepowder, and the slump loss is represented by “cm”, the compressionstrength by “N/mm²”, the adiabatic temperature increase by “° C.”, andthe neutralization depth by “mm”.

TEST EXAMPLE 2

The test was carried out in the same manner as in Test Example 1 exceptthat concretes having concrete blend compositions as shown in Table 2were prepared by using slowly cooled slag powders shown in Table 2,which are the same in the Blaine value and the degree of vitrificationand which are different only in the melilite lattice constant a. Theresults are also shown in Table 2.

Materials used Slag powder (9): Slowly cooled slag powder, CO₂absorption: 4%, amount of bound water: 3%, degree of vitrification: 5%,melilite lattice constant a: 7.73, Blaine value: 6,000 cm²/g, density:3.03 g/cm³ Slag powder (10): Slowly cooled slag powder, CO₂ absorption:4.5%, amount of bound water: 3%, degree of vitrification: 5%, melilitelattice constant a: 7.75, Blaine value: 6,000 cm²/g, density: 3.01 g/cm³Slag powder (11): Slowly cooled slag powder, CO₂ absorption: 4.5%,amount of bound water: 3%, degree of vitrification: 5%, melilite latticeconstant a: 7.80, Blaine value: 6,000 cm²/g, density: 2.98 g/cm³ Slagpowder (12): Slowly cooled slag powder, CO₂ absorption: 4%, amount ofbound water: 3%, degree of vitrification: 5%, melilite lattice constanta: 7.83, Blaine value: 6,000 cm²/g, density: 2.96 g/cm³

TABLE 2 Unit weight (kg/cm³) Adiabatic Test Slag Slump Compressiontemperature Neutralization No. Cement Water Sand Gravel powder lossstrength increase depth Notes 2-1 245 175 804 951  (9)105 7.5 24.5 34.822.0 Ex. 2-2 245 175 804 951 (10)105 7.5 24.2 34.7 20.5 Ex. 1-4 245 175804 951  (4)105 7.0 24.4 34.8 18.5 Ex. 2-3 245 175 804 951 (11)105 7.024.7 34.8 19.0 Ex. 2-4 245 175 804 951 (12)105 7.0 24.9 34.9 19.5 Ex.2-5 245 175 804 951 * 105 7.0 24.9 34.9 42.5 Comp. Ex. Symbol * for slagpowder means fine limestone powder, and the slump loss is represented by“cm”, the compression strength by “N/mm²”, the adiabatic temperatureincrease by “° C.”, and the neutralization depth by “mm”.

TEST EXAMPLE 3

50 parts of water and 300 parts of sand were mixed to 100 parts of acement composition comprising 65 parts of Portland cement shown in Table3 and 35 parts of slag powder (2), to prepare a mortar, whereuponmeasurement of the compression strength was carried out. The results arealso shown in Table 3.

Materials used Cement B: High-early-strength Portland cementmanufactured by Denki Kagaku Kogyo Kabushiki Kaisha, C₃S content: 65%,Blaine value: 4,400 cm²/g Cement C: Mixture comprising 50 parts ofCement A and 50 parts of Cement B, C₃S content: 60%, Blaine value: 3,800cm²/g Sand: JIS standard sand (in accordance with ISO679) Measuringmethod Compressing strength: Measured in accordance with JIS R 5201.

TABLE 3 Test Slag Compression strength No. Cement powder 1 day 3 days 7days Notes 3-1 A Nil 10.5 23.0 41.0 Comp. Ex. 3-2 A 35  7.9 16.2 29.3Ex. 3-3 B 35 13.3 26.4 44.9 Ex. 3-4 C 35 11.8 24.7 43.0 Ex.The slag powder is represented by “parts” per 100 parts of the powder,and the compression strength is represented by “N/mm²”

TEST EXAMPLE 4

This test was carried out in the same manner as in Test Example 3 exceptthat using Cement B, the slowly cooled slag powder (2) shown in Table 4was used in 100 parts of a cement composition comprising Cement B andthe slag powder. The results are also shown in Table 4.

TABLE 4 Test Slag Compression strength No. Cement powder 1 day 3 days 7days Notes 3-1 A Nil 10.5 23.0 41.0 Comp. Ex. 4-1 B 10 19.5 39.2 54.1Ex. 4-2 B 20 18.3 36.2 51.3 Ex. 4-3 B 30 15.3 31.8 47.1 Ex. 3-3 B 3513.3 26.4 44.9 Comp. Ex. 4-4 B 40 12.6 25.7 44.3 Ex. 4-5 B 50 11.6 24.943.2 Ex.The slag powder is represented by “parts” per 100 parts of the powder,and the compression strength is represented by “N/mm²”

TEST EXAMPLE 5

The test was carried out in the same manner as in Test Example 1 exceptthat using Cement A, high fluidity concretes having concrete blendcompositions as identified in Table 5 were prepared, and thesegregation, slump loss, autogenous shrinkage, adiabatic temperatureincrease, compression strength and neutralization depth were measured.

Further, a water reducing agent was used in combination so that theslump flow value of the concretes would be 600±50 mm. The results arealso shown in Table 5.

Measuring methods Segregation: Visually observed. A case wheresegregation resulted, is represented by x, a case where slightsegregation was observed, is represented by Δ, and a case where nosegregation resulted, is represented by o. Slump flow: Spreading ofconcrete was measured at two points in right angle directions inaccordance with “Underwater Non-separable Concrete Manual, Appendix 1“Test On Underwater Non-separable Concrete, Test On Slump Flow”,published by Foundation, Coastal Development Technical Center and theJapanese Institute of Technology on Fishing Ports and Communities, andthe average value was taken as the slump flow. Autogenous Measured inaccordance with the report by shrinkage: JCI autogenous shrinkage studycommittee. It is represented as an autogenous shrinkage strain at amaterial age of 56 days.

TABLE 5 Slump Unit weight (kg/cm³) flow Adiabatic Test Slag 0 60Autogenous Temperature Compression Neutralization No. Cement Water SandGravel powder Segregation min min shrinkage increase strength depthNotes 5-1 300 165 769 839 (1)250 Δ 665 680 −50 41.8 52.0 4.5 Ex. 5-2 300165 769 839 (2)250 ◯ 670 680 −40 41.8 53.5 3.0 Ex. 5-3 300 165 769 839(3)250 ◯ 675 685 −40 41.9 54.0 3.0 Ex. 5-4 300 165 769 839 (4)250 ◯ 675685 −40 42.0 54.5 2.5 Ex. 5-5 300 165 769 839 (5)250 ◯ 670 685 −40 42.255.0 2.0 Ex. 5-6 300 165 767 837 (6)250 ◯ 675 655 −110  44.0 60.5 1.0Ex. 5-7 300 165 766 836 (7)250 ◯ 675 555 −220  47.3 70.1 0.5 Ex. 5-8 300165 765 835 (8)250 ◯ 685 390 −380  66.5 79.8 1.0 Comp. Ex. 5-9 300 165757 826 * 250 ◯ 680 410 −40 42.3 55.0 12.5 Comp. Ex. The slump flow isrepresented by “mm”, the autogenous shrinkage by a strain “×10⁻⁶”, theadiabatic temperature increase by “° C.”, the compression strength by“N/mm²”, and the neutralization depth by “mm” and * for the slag powdermeans fine limestone powder.

TEST EXAMPLE 6

This test was carried out in the same manner as in Test Example 5 exceptthat using the slag powder (4), the concrete blend composition as shownin Table 6 was used. The results are also shown in Table 6.

TABLE 6 Slump Unit weight (kg/cm³) flow Adiabatic Test Slag 0 60Autogenous Temperature Compression Neutralization No. Cement Water SandGravel powder Segregation min min shrinkage increase strength depthNotes 6-1 250 165 768 838 300 ◯ 680 690 +70 36.8 41.2 3.0 Ex. 6-2 275165 768 838 275 ◯ 675 685 −10 39.4 49.1 3.0 Ex. 5-4 300 165 769 839 250◯ 675 685 −40 41.8 53.5 3.0 Ex. 6-3 325 165 769 839 225 ◯ 670 670 −9044.4 57.0 2.5 Ex. 6-4 350 165 769 839 200 ◯ 670 660 −150  46.8 62.5 2.0Ex. 6-5 450 165 771 842 100 ◯ 675 600 −250  56.9 71.5 0.0 Ex. 6-6 550165 773 844  0 ◯ 650 380 −390  66.7 80.4 0.0 Comp. Ex. 6-7 300 165 873953  0 X — — — — — — Comp. Ex. 6-8 300 125 820 895 250 ◯ 690 680 −120 41.8 64.0 0.0 Ex. 6-9 300 175 757 826 250 ◯ 685 660 −10 42.0 49.0 3.5Ex. 6-10 300 200 725 792 250 ◯ 670 610 +110  42.2 33.5 6.5 Ex. 6-11 300225 694 757 250 ◯ 640 550 +150  42.3 28.0 12.0 Ex. 6-12 300 165 759 828275 ◯ 670 680 −40 41.9 53.9 2.5 Ex. 6-13 300 165 748 817 300 ◯ 670 680−40 42.1 54.2 2.0 Ex. 6-14 300 165 738 805 325 ◯ 665 680 −50 42.4 54.71.5 Ex. 6-15 300 165 727 794 350 ◯ 665 680 −50 42.6 55.0 1.0 Ex. Theslump flow is represented by “mm”, the autogenous shrinkage by a strain“× 10⁻⁶”, the adiabatic temperature increase by “° C.”, the compressionstrength by “N/mm²”, and the neutralization depth by “mm” and symbol —for the autogenous shrinkage in Test No. 1-7 means that segregationresulted, so that high fluidity concrete was not prepared.

TEST EXAMPLE 7

Using Cement A, concrete having a concrete blend composition asidentified in Table 5 was prepared, and measurement of the slump losswas carried out and the hexavalent chromium-reducing ability of the slagpowder was evaluated by measuring the hexavalent chromium-remainingconcentration. The results are also shown in Table 7.

Further, a water reducing agent was used so that the slump value of theconcrete would be 18±1.5 cm.

Materials used Slag powder (13): Slowly cooled slag powder, non-sulfuric acid form sulfur: 0.9%, degree of vitrification: 5%, Blainevalue: 4,000 cm²/g, density: 3.00 g/cm³ Slag powder (14): Slowly cooledslag powder, non- sulfuric acid form sulfur: 0.9%, degree ofvitrification: 5%, Blaine value: 4,500 cm²/g, density: 3.00 g/cm³ Slagpowder (15): Slowly cooled slag powder, non- sulfuric acid form sulfur:0.9%, degree of vitrification: 5%, Blaine value: 5,000 cm²/g, density:3.00 g/cm³ Slag powder (16): Slowly cooled slag powder, non- sulfuricacid form sulfur: 0.9%, degree of vitrification: 5%, Blaine value: 6,000cm²/g, density: 3.00 g/cm³ Slag powder (17): Slowly cooled slag powder,non- sulfuric acid form sulfur: 0.9%, degree of vitrification: 5%,Blaine value: 8,000 cm²/g, density: 3.00 g/cm³ Slag powder (18): Oneobtained by immersing slag powder (16) in water for aging to bring thenon-sulfuric acid form sulfur to be 0.7%, degree of vitrification: 5%,Blaine value: 6,000 cm²/g, density: 3.00 g/cm³ Slag powder (19): Oneobtained by immersing slag powder (16) in water for aging to bring thenon-sulfuric acid form sulfur to be 0.5%, degree of vitrification: 5%,Blaine value: 6,000 cm²/g, density: 3.00 g/cm³ Slag powder (20): Oneobtained by immersing slag powder (16) in water for aging to bring thenon-sulfuric acid form sulfur to be 0.3%, degree of vitrification: 5%,Blaine value: 6,000 cm²/g, density: 3.00 g/cm³ Slag powder (21): Slowlycooled slag powder, non- sulfuric acid form sulfur: 0.7%, degree ofvitrification: 10%, Blaine value: 6,000 cm²/g, density: 2.97 g/cm³ Slagpowder (22): Slowly cooled slag powder, non- sulfuric acid form sulfur:0.5%, degree of vitrification: 30%, Blaine value: 6,000 cm²/g, density:2.94 g/cm³ Slag powder (23): Granulated blast furnace slag powder,non-sulfuric acid form sulfur: 0.1%, degree of vitrification: 95%,Blaine value: 6,000 cm²/g, density: 2.90 g/cm³Measuring MethodHexavalent Chromium-Remaining Concentration:

In order to confirm the hexavalent chromium-reducing ability of thecement admixture, a hexavalent chromium standard solution was diluted toprepare a solution having a hexavalent chromium concentration of 100mg/l, and 10 g of each cement admixture was put into 50 cc of thishexavalent chromium solution, followed by stirring. Upon expiration ofseven days, solid-liquid separation was carried out, and the remaininghexavalent chromium concentration in the liquid phase was measured andevaluated. Here, the remaining concentration of hexagonal chromium wasmeasured by an ICP emission spectrochemical analysis in accordance withJIS K 0102.

TABLE 7 Hexavalent Unit weight (kg/cm³) chromium Test Slag Slumpremaining No. Cement Water Sand Gravel powder loss concentration Notes7-1 245 175 804 951 (13)105 8.5  9 Ex. 7-2 245 175 804 951 (14)105 7.5 6 Ex. 7-3 245 175 804 951 (15)105 6.5  3 Ex. 7-4 245 175 804 951(16)105 6.0 ND Ex. 7-5 245 175 804 951 (17)105 5.0 ND Ex. 7-6 245 175804 951 (18)105 7.0 17 Ex. 7-7 245 175 804 951 (19)105 8.0 35 Ex. 7-8245 175 804 951 (20)105 10.0 68 Comp. Ex. 7-9 245 175 804 951 (21)1057.0 19 Ex. 7-10 245 175 803 950 (22)105 8.5 38 Ex. 7-11 245 175 803 950(23)105 11.5 82 Comp. Ex. 7-12 245 175 799 946 * 105 11.5 100  Comp. Ex.The slump loss is represented by “cm” and the hexavalent chromiumremaining concentration by “mg/l”, and symbol * for the slag means finelimestone powder, and ND for the hexavalent chromium remainingconcentration means “not detected”.

TEST EXAMPLE 8

This test was carried out in the same manner as in Test Example 7 exceptthat using the slag powder (16) as identified in Table 8, concreteshaving concrete blend compositions as identified in Table 8 wereprepared, and the slump loss was measured. The results are also shown inTable 8.

TABLE 8 Unit weight (kg/cm³) Test Slag Slump No. Cement Water SandGravel powder loss 8-1 339 175 806 954 11 11.5  8-2 332 175 806 954 1810.5  8-3 315 175 805 953 35 9.5 8-4 280 175 805 952 70 8.5 8-5 210 175803 950 140  5.0 8-6 175 175 803 950 175  4.0 8-7 140 175 802 949 210 3.0 Slump loss is represented by “cm”

TEST EXAMPLE 9

This test was carried out in the same manner as in Example 7 except thatusing cement A as identified in Table 9, high fluidity concretes havingconcrete blend compositions as identified in Table 9, were prepared, andsegregation and a change with time of slump flow were measured. Theresults are also shown in Table 9.

Further, a water reducing agent was used in combination so that theslump flow value of the concretes would be 600±50 mm.

Measuring methods Segregation: Visually observed. A case wheresegregation resulted is represented by x, a case where slightsegregation was observed, is represented by Δ, and a case where nosegregation resulted, is represented by o. Slump flow: Spreading ofconcrete was measured at two points in right angle directions inaccordance with “Underwater Non-separable Concrete Manual, Appendix 1“Test On Underwater Non-separable Concrete, Test On Slump Flow”,published by Foundation, Coastal Development Technical Center and theJapanese Institute of Technology on Fishing Ports and Communities, andthe average value was taken as the slump flow.

TABLE 9 Unit weight (kg/cm³) Slump flow Test Slag 0 60 120 No. CementWater Sand Gravel powder Segregation min min min Notes 9-1 300 165 769839 (13)250 Δ 665 680 550 Ex. 9-2 300 165 769 839 (14)250 ◯ 670 680 560Ex. 9-3 300 165 769 839 (15)250 ◯ 675 685 570 Ex. 9-4 300 165 769 839(16)250 ◯ 675 685 605 Ex. 9-5 300 165 769 839 (17)250 ◯ 670 685 625 Ex.9-6 300 165 769 839 (18)250 ◯ 680 675 580 Ex. 9-7 300 165 769 839(19)250 ◯ 670 660 525 Ex. 9-8 300 165 769 839 (20)250 ◯ 670 550 370Comp. Ex. 9-9 300 165 767 837 (21)250 ◯ 675 670 560 Ex. 9-10 300 165 766836 (22)250 ◯ 675 655 510 Ex. 9-11 300 165 765 835 (23)250 ◯ 685 390 —Comp. Ex. 9-12 300 165 757 826 * 250 ◯ 680 410 — Comp. Ex. Symbol * forslag means fine limestone powder, and symbol — for slump flow means “notmeasurable”.

TEST EXAMPLE 10

This test was carried out in the same manner as in Test Example 1 exceptthat concretes having concrete blend compositions as identified in Table10 were prepared, and the slump loss, compression strength, adiabatictemperature increase, neutralization depth, further, effects of thepresent cement admixture for reducing hexavalent chromium, were measuredby prescribed methods. The results are also shown in Table 10.

Materials used Slag powder (24): Slowly cooled slag powder, CO₂absorption: 2.0%, amount of bound water: 2.0%, non-sulfuric acid formsulfur: 0.9%, soluble sulfur concentration: 300 mg/l, oxygenconsumption: 7.5 × 10⁻³ mmolO₂/g, oxidation-reduction potential: 225 mV,degree of vitrification: 5%, melilite lattice constant a: 7.78, Blainespecific surface area: 4,000 cm²/g, density: 3.00 g/cm³. Slag powder(25): Slowly cooled slag powder, CO₂ absorption: 3.0%, amount of boundwater: 2.5%, non-sulfuric acid form sulfur: 0.9%, soluble sulfurconcentration: 340 mg/l, oxygen consumption: 9.2 × 10⁻³ mmolO₂/g,oxidation-reduction potential: 246 mV, degree of vitrification: 5%,melilite lattice constant a: 7.78, Blaine specific surface area: 4,500cm²/g, density.: 3.00 g/cm³. Slag powder (26): Slowly cooled slagpowder, CO₂ absorption: 3.5%, amount of bound water: 2.7%, non-sulfuricacid form sulfur: 0.9%, soluble sulfur concentration: 380 mg/l, oxygenconsumption: 9.6 × 10⁻³ mmolO₂/g, oxidation-reduction potential: 270 mV,degree of vitrification: 5%, melilite lattice constant a: 7.78, Blainespecific surface area: 5,000 cm²/g, density: 3.00 g/cm³. Slag powder(27): Slowly cooled slag powder, CO₂ absorption: 4.0%, amount of boundwater: 3.0%, non-sulfuric acid form sulfur: 0.9%, soluble sulfurconcentration: 418 mg/l, oxygen consumption: 10.3 × 10⁻³ mmolO₂/g,oxidation-reduction potential: 290 mV, degree of vitrification: 5%,melilite lattice constant a: 7.78, Blaine specific surface area: 6,000cm²/g, density: 3.00 g/cm³. Slag powder (28): Slowly cooled slag powder,CO₂ absorption: 4.5%, amount of bound water: 4.0%, non-sulfuric acidform sulfur: 0.9%, soluble sulfur concentration: 508 mg/l, oxygenconsumption: 12.2 × 10⁻³ mmolO₂/g, oxidation-reduction potential: 350mV, degree of vitrification: 5%, melilite lattice constant a: 7.78,Blaine specific surface area: 8,000 cm²/g, density: 3.00 g/cm³. Slagpowder (29): Slowly cooled slag powder, CO₂ absorption: 4.0%, amount ofbound water: 3.0%, non-sulfuric acid form sulfur: 0.7%, soluble sulfurconcentration: 325 mg/l, oxygen consumption: 7.7 × 10⁻³ mmolO₂/g,oxidation-reduction potential: 230 mV, degree of vitrification: 5%,melilite lattice constant a: 7.78, Blaine specific surface area: 6,000cm²/g, density: 3.00 g/cm³. Slag powder (30): Slowly cooled slag powder,CO₂ absorption: 4.0%, amount of bound water: 3.0%, non-sulfuric acidform sulfur: 0.5%, soluble sulfur concentration: 229 mg/l, oxygenconsumption: 6.3 × 10⁻³ mmolO₂/g, oxidation-reduction potential: 218 mV,degree of vitrification: 5%, melilite lattice constant a: 7.78, Blainespecific surface area: 6,000 cm²/g, density: 3.00 g/cm³. Slag powder(31): Slowly cooled slag powder, CO₂ absorption: 4.0%, amount of boundwater: 3.0%, non-sulfuric acid form sulfur: 0.3%, soluble sulfurconcentration: 138 mg/l, oxygen consumption: 4.2 × 10⁻³ mmolO₂/g,oxidation-reduction potential: 178 mV, degree of vitrification: 5%,melilite lattice constant a: 7.78, Blaine specific surface area: 6,000cm²/g, density: 3.00 g/cm³. Slag powder (32): Slowly cooled slag powder,CO₂ absorption: 4.0%, amount of bound water: 3.5%, non-sulfuric acidform sulfur: 0.7%, soluble sulfur concentration: 375 mg/l, oxygenconsumption: 6.3 × 10⁻³ mmolO₂/g, oxidation-reduction potential: 223 mV,degree of vitrification: 10%, melilite lattice constant a: 7.76, Blainespecific surface area: 6,000 cm²/g, density: 2.97 g/cm³. Slag powder(33): Slowly cooled slag powder, CO₂ absorption: 3.0%, amount of boundwater: 5.0%, non-sulfuric acid form sulfur: 0.5%, soluble sulfurconcentration: 291 mg/l, oxygen consumption: 3.0 × 10⁻³ mmolO₂/g,oxidation-reduction potential: 143 mV, degree of vitrification: 30%,melilite lattice constant a: 7.74, Blaine specific surface area: 6,000cm²/g, density: 2.94 g/cm³. Slag powder (34): Granulated blast furnaceslag, CO₂ absorption: 1.0%, amount of bound water: 9.5%, non-sulfuricacid form sulfur: 0.9%, soluble sulfur concentration: 10 mg/l, oxygenconsumption: 2.0 × 10⁻³ mmolO₂/g, oxidation-reduction potential: 99 mV,degree of vitrification: 95%, Blaine specific surface area: 6,000 cm²/g,density: 2.90 g/cm³.

TABLE 10 Hexavalent Unit weight (kg/cm³) Adiabatic chromium Test SlagSlump Compression temperature Neutralization remaining No. Cement WaterSand Gravel powder loss strength increase depth concentration Notes 10-1245 175 804 951 (24)105 9.5 24.1 33.1 26.5  8 Ex. 10-2 245 175 804 951(25)105 9.0 24.2 33.4 23.5  5 Ex. 10-3 245 175 804 951 (26)105 8.0 24.334.1 20.0  2 Ex. 10-4 245 175 804 951 (27)105 7.0 24.6 34.9 18.0 ND Ex.10-5 245 175 804 951 (28)105 7.0 24.9 35.0 16.0 ND Ex. 10-6 245 175 804951 (29)105 7.5 24.7 34.9 16.5 16 Ex. 10-7 245 175 804 951 (30)105 8.525.0 35.3 15.5 33 Ex. 10-8 245 175 804 951 (31)105 10.0 24.9 35.1 16.060 Comp. Ex. 10-9 245 175 804 951 (32)105 7.0 25.0 35.1 17.5 17 Comp.Ex. 10-10 245 175 804 951 (33)106 8.0 26.0 36.0 17.5 37 Ex. 10-11 245175 804 951 (34)106 11.5 34.0 44.2 — 99 Ex. 10-12 350 175 806 954 — 012.0 33.5 45.5 — — Ex. 10-13 339 175 806 954 (27)11  11.0 33.2 43.1 — —Ex. 10-14 332 175 806 954 (27)18  10.5 32.8 43.0 — — Ex. 10-15 315 175805 953 (27)35  9.5 30.1 40.8 — — Ex. 10-16 280 175 805 952 (27)70  8.028.1 37.0 — — Ex. 10-17 210 175 803 950 (27)140 6.5 22.9 32.1 — — Ex.10-18 175 175 803 950 (27)175 5.5 21.3 28.6 — — Ex. 10-19 140 175 802949 (27)210 4.0 18.7 24.8 — — Ex. 10-20 245 175 804 951 * 105 11.5 24.834.5 42.5 100  Comp. Ex. Symbol * for slag powder means fine limestonepowder, and the slump loss is represented by “cm”, the compressionstrength by “N/mm²”, the adiabatic temperature increase by “° C.”, theneutralization depth by “mm”, and the hexavalent chromium remainingconcentration by “mg/l”, and ND for the hexavalent chromium remainingconcentration means “not detected”.

TEST EXAMPLE 11

This test was carried out in the same manner as in Test Example 10except that concretes having blend compositions as identified in Table11 were prepared by using various slowly cooled slag powders which arethe same in the known sulfuric acid form sulfur amount, soluble sulfurconcentration, degree of vitrification and grain value and which aredifferent only in the melilite lattice constant a. The results are alsoshown in Table 11.

Materials used Slag powder (35): Slowly cooled slag powder, CO₂absorption: 4.0%, amount of bound water: 3%, non-sulfuric acid formsulfur: 0.9%, soluble sulfur concentration: 508 mg/l, degree ofvitrification: 5%, melilite lattice constant a: 7.73, Blaine specificsurface area: 6,000 cm²/g, density: 3.03 g/cm³. Slag powder (36): Slowlycooled slag powder, CO₂ absorption: 4.5%, amount of bound water: 3%,non-sulfuric acid form sulfur: 0.9%, soluble sulfur concentration: 508mg/l, degree of vitrification: 5%, melilite lattice constant a: 7.75,Blaine specific surface area: 6,000 cm²/g, density: 3.01 g/cm³. Slagpowder (37): Slowly cooled slag powder, CO₂ absorption: 4.5%, amount ofbound water: 3%, non-sulfuric acid form sulfur: 0.9%, soluble sulfurconcentration: 508 mg/l, degree of vitrification: 5%, melilite latticeconstant a: 7.80, Blaine specific surface area: 6,000 cm²/g, density:2.98 g/cm³. Slag powder (38): Slowly cooled slag powder, CO₂ absorption:4.0%, amount of bound water: 3%, non-sulfuric acid form sulfur: 0.9%,soluble sulfur concentration: 508 mg/l, degree of vitrification: 5%,melilite lattice constant a: 7.83, Blaine specific surface area: 6,000cm²/g, density: 2.96 g/cm³.

TABLE 11 Hexavalent Unit weight (kg/cm³) Adiabatic chromium Test SlagSlump Compression temperature Neutralization remaining No. Cement WaterSand Gravel powder loss strength increase depth concentration Notes 11-1245 175 804 951 (35)105 7.0 24.7 34.7 21.5 ND Ex. 11-2 245 175 804 951(36)105 7.5 24.4 34.8 20.5 ND Ex. 10-4 245 175 804 951 (27)105 7.0 24.634.9 18.0 ND Ex. 11-3 245 175 804 951 (37)106 7.5 24.2 34.9 19.5 ND Ex.11-4 245 175 804 951 (38)107 7.0 24.8 34.5 20.0 ND Ex. The slump loss isrepresented by “cm”, the compression strength by “N/mm²”, the adiabatictemperature increase by “° C.”, the neutralization depth by “mm”, and NDfor the hexavalent chromium remaining concentration means “notdetected”.

TEST EXAMPLE 12

This test was carried out in the same manner as in Test Example 3 exceptthat 65 parts of the Portland cement as identified in Table 12 and 35parts of the slag powder (25) were used. The results are also shown inTable 12.

TABLE 12 Test Slag Compression strength No. Cement powder 1 day 3 days 7days Notes  3-1 A Nil 10.5 23.0 41.0 Comp. Ex. 12-1 A 35 8.0 16.6 29.9Ex. 12-2 B 35 13.0 26.6 45.0 Ex. 12-3 C 35 11.9 24.0 43.3 Ex.The slag powder is represented by “parts” per 100 parts of the powder,and the compression strength is represented by “N/mm²”.

TEST EXAMPLE 13

This test was carried out in the same manner as in Test Example 4 exceptthat cement B was used, and the slowly cooled slag powder (25) asidentified in Table 13 was used in 100 parts of the cement compositioncomprising the cement and the slag powder. The results are also shown inTable 13.

TABLE 13 Test Slag Compression strength No. Cement powder 1 day 3 days 7days Notes  3-1 A Nil 10.5 23.0 41.0 Comp. Ex. 13-1 B 10 19.4 39.1 54.3Ex. 13-2 B 20 18.0 35.8 50.5 Ex. 13-3 B 30 15.5 32.0 47.0 Ex. 12-2 B 3513.0 26.6 45.0 Comp. Ex. 13-4 B 40 12.5 24.9 44.2 Ex. 13-5 B 50 11.724.5 43.0 Ex.The slag powder is represented by “parts” per 100 parts of the powder,and the compression strength is represented by “N/mm²”.

TEST EXAMPLE 14

This test was carried out in the same manner as in Test Example 5 exceptthat the slowly cooled slag powder as identified in Table 14 was used.The results are also shown in Table 14.

TABLE 14 Unit weight (kg/cm³) Slump flow Adiabatic Test Slag Seg- 0 60Autogenous Temperature Compression Neutralization No. Cement Water SandGravel powder regation min min shrinkage increase strength depth Notes14-1 300 165 769 839 (24) 250 Δ 660 670 −40 41.5 52.3 4.5 Ex. 14-2 300165 769 839 (25) 250 ◯ 665 675 −30 41.5 53.6 3.5 Ex. 14-3 300 165 769839 (26) 250 ◯ 670 675 −30 41.8 54.2 3.0 Ex. 14-4 300 165 769 839 (27)250 ◯ 675 675 −30 42.1 54.6 2.5 Ex. 14-5 300 165 769 839 (28) 250 ◯ 675675 −30 42.3 55.1 2.0 Ex. 14-6 300 165 767 837 (29) 250 ◯ 670 670 −3041.8 54.5 2.0 Ex. 14-7 300 165 766 836 (30) 250 ◯ 665 660 −30 41.9 54.02.0 Ex. 14-8 300 165 766 836 (31) 250 ◯ 660 540 −30 42.1 54.0 2.5 Ex.14-9 300 165 766 836 (32) 250 ◯ 670 660 −100 43.1 60.3 1.5 Ex.  14-10300 165 766 836 (33) 250 ◯ 670 550 −200 47.0 70.0 0.5 Ex.  14-11 300 165765 835 (34) 250 ◯ 675 395 −380 66.9 79.7 1.5 Comp. Ex.  5-9 300 165 757826 * 250 ◯ 680 410 −40 42.3 55.0 12.5 Comp. Ex. slump flow isrepresented by “mm”, the autogenous shrinkage by a strain “×10⁻⁶”, theadiabatic temperature increase by “° C.”, the compression strength by“N/mm²”, and the neutralization depth by “mm” and symbol * for slagpowder means fine limestone powder

TEST EXAMPLE 15

This test was carried out in the same manner as in Test Example 6 exceptthat the slowly cooled slag powder (36) was used. The results are alsoshown in Table 15.

TABLE 15 Unit weight (kg/cm³) Slump flow Adiabatic Test Slag Seg- 0 60Autogenous Temperature Compression Neutralization No. Cement Water SandGravel powder regation min min shrinkage increase strength depth Notes15-1 250 165 768 838 (27) 300 ◯ 685 685 +50 36.7 43.5 2.5 Ex. 15-2 275165 768 838 (27) 275 ◯ 680 680 −20 38.4 50.2 2.5 Ex. 14-4 300 165 769839 (27) 250 ◯ 675 675 −30 42.1 54.6 2.5 Ex. 15-3 325 165 769 839 (27)225 ◯ 675 675 −100 44.0 56.0 2.5 Ex. 15-4 350 165 769 839 (27) 200 ◯ 675660 −160 46.3 62.5 2.5 Ex. 15-5 450 165 771 842 (27) 100 ◯ 670 590 −24056.6 70.3 0.5 Ex. 15-6 550 165 773 844 — 0 ◯ 655 375 −370 66.5 78.3 0.5Comp. Ex. 15-7 300 165 873 953 — 0 X — — — — — — Comp. Ex. 15-8 300 125820 895 (27) 250 ◯ 695 675 −130 42.0 63.5 0.0 Ex. 15-9 300 175 757 826(27) 250 ◯ 690 665 −20 42.1 48.8 3.0 Ex.  15-10 300 200 725 792 (27) 250◯ 680 615 +100 42.2 34.0 5.5 Ex.  15-11 300 225 694 757 (27) 250 ◯ 650560 +140 42.2 29.0 11.0 Ex.  15-12 300 165 759 828 (27) 275 ◯ 665 670−50 42.3 53.4 2.5 Ex.  15-13 300 165 748 817 (27) 300 ◯ 665 660 −50 42.053.9 3.0 Ex.  15-14 300 165 738 805 (27) 325 ◯ 670 665 −40 42.3 53.7 2.0Ex.  15-15 300 165 727 794 (27) 350 ◯ 665 670 −50 42.1 54.0 1.5 Ex. Theslump flow is represented by “mm”, the autogenous shrinkage by a strain“× 10⁻⁶”, the adiabatic temperature increase by “° C.”, the compressionstrength by “N/mm²”, and the neutralization depth by “mm” and symbol —for the autogenous shrinkage in Test No. 1-7 means that segregationresulted, so that high fluidity concrete was not prepared.

TEST EXAMPLE 16

This test was carried out in the same manner as in Test Example 7 exceptthat the hexavalent chromium-reducing effect of the slag was evaluatedby mixing a reducing agent (ferrous sulfate, guaranteed reagent,manufactured by Kanto Chemical Co., Inc.) as identified in Table 8 tothe above slag powder (14). The results are shown in Table 16.

TABLE 16 Hexavalent Slag Reducing chromium powder agent remaining (partsby (parts by concentration Test No. weight) weight) (mg/l) Notes 16-1 5050 ND Ex. 16-2 90 10 ND Ex. 16-3 95 5 ND Ex. 16-4 99 1 2 Ex.  7-2 100 06 Comp. Ex.

INDUSTRIAL APPLICABILITY

By using the cement admixture of the present invention, the amount ofclinker to be incorporated can be reduced, whereby a low environmentalload type cement composition can be obtained, and by using such a cementcomposition, it is possible to obtain a concrete which has a small slumploss or heat of hydration and which is hardly neutralized.

Further, even when applied to a concrete having a low water/powder ratiosuch as a high fluidity concrete, it is possible to suppress autogenousshrinkage to a small level.

Further, an effect to reduce hexavalent chromium, will also be obtained.

1. A cement admixture, comprising a slowly cooled slag powder, wherein:the slowly cooled slag powder contains melilite as its main component;the slowly cooled slag powder has a carbon dioxide absorption of atleast 2% when carbonated for 7 days in air having a carbon dioxideconcentration of 5%, a temperature of 30° C. and a relative humidity of60%; and the slowly cooled slag powder has a melilite lattice constantof from 7.75 to 7.82.
 2. A cement admixture, comprising a slowly cooledslag powder, wherein: the slowly cooled slag powder contains melilite asits main component; the slowly cooled slag powder has a loss on ignitionof at most 5%, loss on ignition being a weight reduction when ignited at1,000° C. for 30 minutes; and the slowly cooled slag powder has amelilite lattice constant of from 7.75 to 7.82.
 3. A cement admixture,comprising: a slowly cooled slag powder, wherein: the slowly cooled slagpowder contains melilite as its main component; the slowly cooled slagpowder contains at least 0.5% of sulfur of a non-sulfuric acid form; andthe slowly cooled slag powder has a melilite lattice constant of from7.75 to 7.82.
 4. A cement admixture, comprising a slowly cooled slagpowder, wherein: the slowly cooled slag powder contains melilite as itsmain component; the slowly cooled slag powder has an ion concentrationof non-sulfuric acid form sulfur to elute, of at least 100 mg/l; and theslowly cooled slag powder has a melilite lattice constant of from 7.75to 7.82.
 5. The cement admixture according to claim 1, wherein theslowly cooled slag powder has a loss on ignition of at most 5%, loss onignition being a weight reduction when ignited at 1,000° C. for 30minutes.
 6. The cement admixture according to claim 1, wherein theslowly cooled slag powder contains at least 0.5% of sulfur present in anon-sulfuric acid form.
 7. The cement admixture according to claim 1,wherein the slowly cooled slag powder has a concentration ofnon-sulfuric acid form sulfur to elute, of at least 100 mg/l.
 8. Thecement admixture according to claim 1, wherein the slowly cooled slagpowder has a degree of vitrification of at most 30%.
 9. The cementadmixture according to claim 1, wherein the slowly cooled slag powderhas a Blaine specific surface area of at least 4000 cm²/g.
 10. Thecement admixture according to claim 1, wherein the admixture has anoxygen consumption of at least 2.5×10⁻³ mmol O₂/g.
 11. The cementadmixture according to claim 1, wherein the admixture has anoxidation-reduction potential of at least 100 mV.
 12. A cementcomposition comprising the cement admixture according to claim
 1. 13.The cement composition according to claim 12, wherein the cementcomprises Portland cement having a 3CaO.SiO₂ content of at least 60 wt%.
 14. Cement concrete comprising the cement composition according toclaim
 12. 15. The cement concrete according to claim 14, wherein theconcrete has a slump flow of 650±50 mm.
 16. Cement concrete comprisingthe cement composition according to claim
 13. 17. The cement admixtureaccording to claim 1, wherein: the slowly cooled slag powder has a losson ignition of at most 5%, loss on ignition being a weight reductionwhen ignited at 1,000° C. for 30 minutes; and the slowly cooled slagpowder contains at least 0.5% of sulfur of a non-sulfuric acid form. 18.The cement admixture according to claim 3, wherein the slowly cooledslag powder has a loss on ignition of at most 5%, loss on ignition beinga weight reduction when ignited at 1,000° C. for 30 minutes.
 19. Thecement admixture according to claim 4, wherein the slowly cooled slagpowder has a loss on ignition of at most 5%, loss on ignition being aweight reduction when ignited at 1,000° C. for 30 minutes.